1. Field of the Invention
The present invention pertains generally to problems of character and instruction message encoding incompatibility that may arise between two different data processing systems when they have to communicate together. For example, one of the systems is a microcomputer or terminal knowing a given character alphabet and message structure and the other is a central electronic system knowing different alphabets and message structures.
2. Description of the Prior Art
At present a broad range of terminals, microcomputers and electronic systems are available which do not always use the same character alphabet, the same exchange protocol to transmit and receive, or the same message structure. This incompatibility between these different equipments often makes it impossible to interconnect them in order to produce higher level equipment or systems.
Equipments which should be compatible and adaptable are often in fact incompatible, such as terminals mostly equipped with a keyboard having keys determining program functions to which encoding combinations are attributed, fixed arbitrarily by the manufacturer. Certain terminals make use of specific order codes, respectively for their internal management and management of devices connected to them. These terminals connected to a central electronic system, not knowing the same order codes, operate incompletely. Moreover, the constant evolution in data processing techniques contributes to the development of different types of terminal, notably color display terminals, thus making incompatibility problems more difficult.
With the existing standardization, standard exchange protocols are available, such as the ANSI, VT52, VT100 or the videotex standard. These protocols have the advantage of making the equipments adaptable for certain types of exchanges but very often reduce the area of use of the high performance equipments.
Moreover, the range of existing standardized alphabets is evolving perpetually in order to meet the different national requirements and adapt to the new technological possibilities. Thus different binary encoding combinations can correspond to the same character, according to the standardized alphabet used.